ABC News anchor Diane Sawyer joined Megyn Kelly tonight to discuss her exclusive, eye-opening interview with Sue Klebold, the mother of one of the Columbine shooters.

Sawyer said that Klebold, who has remained silent for 17 years after the tragic school shooting that left 15 dead, including her son and the other killer, shared the "shattering lessons" that she has learned.

Sawyer said that one striking thing that Klebold revealed was that both she and her son were keeping journals at the same time. While Klebold was writing about adolescent phases and her son's happier times, he was writing about his suicidal depression.